1. Field of the Invention
This invention relates generally to circuit breakers and, more particularly, to circuit breakers of the electromagnetic type including an operating mechanism having a linkage mechanism with a pair of links and a lock.
2. Background Information
Circuit breakers of the electromagnetic type are shown, for example, in U.S. Pat. Nos. 3,329,913; and 4,151,386.
Such electromagnetic circuit breakers typically comprise a movable contact, which is mounted on a movable arm, and a fixed or stationary contact. An operating handle is coupled to the movable arm via a linkage mechanism, part of which comprises a collapsible toggle assembly including a first or catch link, a second or U-link, and a lock for the first and second links. The movable and stationary contacts are operated between contacts xe2x80x9copenxe2x80x9d and contacts xe2x80x9cclosedxe2x80x9d positions by pivoting the operating handle. The circuit breaker further comprises an electromagnetic device which, in response to one or more predetermined electrical conditions, pivots the lock in order to break the first and second links and trip xe2x80x9copenxe2x80x9d the separable movable and stationary contacts. The lock is disposed substantially external to the U-link between the U-link and the operating mechanism frame. The U-link has a stop surface and a pivot point for the lock. The lock has a latch surface, which latches a mating surface of the catch link.
A known magneto-hydraulic circuit breaker employs an early (i.e., relative to handle throw) toggle-on point. At the point where the operating mechanism toggles and the unbroken linkage mechanism begins to move, there is very little energy stored in the operating mechanism springs. As a result, the circuit breaker can be xe2x80x9cteasedxe2x80x9d on, which causes undesirable and potentially damaging arcing to the separable contacts.
xe2x80x9cSlow makexe2x80x9d is defined as the closing velocity of the circuit breaker separable contacts being directly dependent upon the closing speed of the operating handle. For a circuit breaker operating at relatively high voltages (e.g., 480 to 600 VAC), this results in a greater tendency for the separable contacts to weld closed, and significantly reduces the number of switching operations in the operating life of the circuit breaker.
U.S. patent application Ser. No. 10/185,858, filed Jun. 27, 2002, discloses a circuit breaker including a pivot lever having a first arm with a first end adapted for engagement with a movable contact arm, and a second arm having a second end adapted for engagement with an operating handle assembly. The first end of the pivot lever carries a U-shaped hook member pivotally disposed thereon. The hook member has a J-shaped hook, which is adapted for engagement with the movable contact arm, and a J-shaped pivot end, which is pivotally mounted in an opening of the first arm. In order to eliminate the dependency between the movable contact arm and the operating handle assembly, the J-shaped hook initially hooks the movable contact arm. The pivot end of the hook member is inserted into the first or free end of the pivot lever. The pivot lever pivots about a pin and translates the hook member and the movable contact arm movement up to the operating handle assembly. The second or handle end of the pivot lever interacts with a blocking disk of the operating handle assembly, which disk rotates about the same center as the operating handle, but is allowed independent movement.
There is room for improvement in circuit breakers.
These needs and others are met by the present invention, which provides an internal lock system for the first or catch link and the second or U-link of an operating mechanism linkage mechanism. The lock is employed substantially internal to the U-link, in order to provide suitable space on both sides of the U-link for other operating mechanism components, such as extension springs and elongated arms of the operating handle. A lock return spring may also be employed substantially internal to the U-link.
As one aspect of the invention, a circuit breaker comprises: separable contacts; a trip mechanism including a member responsive to at least one selected condition of current flowing through the separable contacts; and an operating mechanism for opening and closing the separable contacts, the operating mechanism including a closed position, a tripped open position, a lock, a first link and a second link having a base and a pair of legs, the lock pivotally mounted to and substantially between the legs of the second link, the first link pivotally mounted to the second link, the first link and the second link having a first state in the closed position and a second state in the tripped open position, the lock maintaining the first state in the closed position and responding to the member of the trip mechanism to release the first link and the second link to the second state in the tripped open position.
The operating mechanism may further include a pivot, with a movable contact arm pivotally mounted to the pivot and carrying one of the separable contacts. A spring member may be disposed between the legs of the second link, with the spring member having a first end and a second end, the first end of the spring member engaging the pivot, the second end of the spring member engaging the lock.
Each of the legs of the second link may include a cutout portion and a pivot portion. The lock may include a pair of ears, with the lock passing through the cutout portions of the legs of the second link before each one of the ears pivotally engages a corresponding one of the pivot portions of the legs of the second link.
The first end of the spring member may include a pair of legs. Each of the legs of the second link may include an opening, with each of the legs of the first end of the spring member passing through a corresponding one of openings of the legs of the second link and engaging the pivot.
The spring member may be formed from a wire including a first L-shaped portion forming a first one of the legs of the first end of the spring member, a U-shaped portion forming the second end of the spring member, and a second L-shaped portion forming a second one of the legs of the first end of the spring member, with each of the first and second L-shaped portions having a leg portion and a foot portion, with each of the foot portions passing through a corresponding one of the openings of the legs of the second link, with the U-shaped portion having a base engaging the lock and a pair of legs, and with each of the legs of the U-shaped portion being coextensive with and forming a bend portion, which engages the pivot, with a corresponding one of the first one and the second one of the legs of the first end of the spring member.
The lock may include a protrusion, and the second end of the spring member may engage the lock at about the protrusion thereof, in order to hold the lock pivotally in place between the legs of the second link.
The legs of the second link may form a stop, and the lock may include a surface opposite the protrusion thereof, with the surface of the lock engaging the stop.